Japanese Utility Model Application Laid-Open No. 4-14536 discloses a tip-up vehicle seat which includes a seat back attached to a vehicle body, a seat bottom rotatably attached to the seat back, and a leg member rotatably attached to the seat bottom. The seat bottom is displaceable between a retracted position where it becomes substantially in parallel with the seat back and an available or horizontal position where it becomes approximately at right angles with the seat back. The leg member is displaceable between a retracted position where it becomes substantially in parallel with the seat bottom and a support position where it becomes approximately at right angles with the seat bottom. The seat bottom is held at the retracted position with a lock mechanism.
For using this vehicle seat, three operations, that is, a first operation of moving the leg member to the support position, a second operation of unlocking the lock mechanism, and a third operation of moving the seat bottom to the available position are necessary. And, the leg member should always be moved to the support position before the seat bottom is moved to the available position. If anyone sits on the seat bottom at the available position while the leg member is not positioned at the support position, the seat bottom may be deformed by large load. Thus, in using, a conventional seat is delicate and troublesome.